Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N31/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic oxygen or sulfur compounds
  • A01N31/02—Acyclic compounds

Definitions

• the present invention relates to stable colloidal dispersions of 1-triacontanol (hereinafter referred to as triacontanol) in water.
• Triaconzanol a C 30 linear, primary alcohol, occurs in natura and can be extracted from alfalfa as a crystalline praduct. It is known in the art to be useful for stimulating growth in a wide variety of plants, including agricultural crops such as corn, soybeans, wheat, rice and tomatoes. However, field testing of various triacontanol formulations has generally produced inconsistent and disappointing results.
• the stable colloidal- dispersions herein are capable of more consistently stimulating plant growth because they allow for the uniform application of a large number of very small crystalline triacontanol particles.
• Formulations are prepared by dissolving the triacontanol in organic solvents such as chloroform or benzene and then adding the solution to water, which can also contain an emulsifying agent.
• the formulations are preferably prepared by dissolving triacontanol in acetone and then mixing the solution with water.
• triacontanol is known to be useful for stimulating plant growth, it is apparent that there is a continuing need for triacontanol formulations capable of more consistently stimulating growth under practical conditions.
• the present invention encompasses stable colloidal dispersions comprising: (a) from about 10 -10 g/1 to about 0.5 g/1 of 1-triacontanol having a mean particle radius of less than about 0.3 microns, and (b) water.
• the invention also encompasses stable colloidal dispersions comprising: (a) from about 10 -10 g/l to about 4 g/1 of 1-triacontanol having a mean particle radius of less than about 0.3 microns, (o) a dispersing agent selected from the group consisting of anionic, cationic, zwitterionic and polyfunctional single bond nonionic surfactants, wherein the dispersing agent is present at a concentration of less than about 5% by weight of the 1-triacontanol and, additionally, is present at a concentration less than its critical micelle concentration wnen it has a hydrocarbyl chain length of less than or equal to aoout 18 carbon atoms, and (c) water.
• the stable colloidal dispersions of the present invention allow for the uniform application of a large number of very small crystalline triacontanol particles, and thus are capable of more consistently stimulating plant growth than are the triacontanol formulations disclosed in the art.
• Otner formulations have been prepared by dissolving the triacontanol in a water-insoluble solvent (e.g., naptha) and then emulsifying with water in the presence of an emulsifying agent.
• a water-insoluble solvent e.g., naptha
• the triacontanol remains dissolved in the solvent where it has low chemical and biological activity. Since the particle number concentration of the dispersed triacontanol solution will 02 small, field applications will also be relatively nonuniform.
• the mixing of the triacontanol solutions witn water in ooth of the aoove described methods typically occurs just prior to field applications so that the triacontanol particle size and particle numoer concentration, and hence uniformity of application, are not known or controlled.
• the dispersions herein have a very small triacontanol particle size, which insures good colloidal stability, and a very large particle number concentration.
• a dispersion of 1 g/1 of 0.1 micron radius particles would contain about 3 x 10 15 particles/I, assuming that the particles are monodisperse, spherical and have a density of 0.82 g/cc.
• the particle number concentration would be 3 x 109/1. Since 200 micron diameter spray droplets encountered in agricultural sprays contain about 4.2 x 10 -9 1, each droplet would contain about 12 triacontanol particles, on average.
• the dispersions of the present invention are initially prepared in the laboratory or plant where the colloidal dimensions (i.e., particle size and number concentration) can be easily measured and controlled. Once formed, the dispersions appear to be indefinitely stable (samples stored at room temperature for a period of 8 montns have not flocculated and appear to be unchanged). For practical and economical reasons, the dispersions herein will typically oe prepared in concentrated form and will then be diluted with water just prior to use to provide a spray solution, nutrient broth, etc. Importantly, dilution of the concentrated dispersions does not alter their colloidal dimensions. And since the triacontanol particles are not surface active, the dilution factor can be very large without loss of material to container surfaces or the air-water interface.
• the colloidal dimensions i.e., particle size and number concentration
• the dispersions herein provide crystalline triacontanol particles whicn have optimum chemical and biological activity and are readily available to the plants because they remain dispersed in the aqueous plant vascular fluids. Due to their small size, the mooility of the triacontanol particles within such aqueous systems is reasonably high (e.g., the mean diffusion coefficient of particles in the dispersions is between 10- 7 and 10 -8 cm 2 sec. -1 ).
• the stability of the present dispersions is determined, in part, by the'size of the dispersed triacontanol particles.
• Particle size is determined herein by a cumulant analysis of the autocorrelation function obtained in a quasi-elastic (dynamic) light scattering (QELS) measurement.
• QE L S is described by Berne and Pecora in Dynamic Light Scattering, J. Wiley & Sons (1976).
• the sample temperatures are controlled, and literature values for the corresponding viscosity and refractive index of water at the controlled temperature are used in computing the particle size.
• the particle size distributions are obtained from a cumulant analysis, of degree either 2 or 3, of tne autocorrelation function by assuming the particles are spherical and obey Stokes-Einstein dynamics. Tnere is, therefore, no kurtosis assumed in the distribution.
• Both a mean particle radius, r, and a value for the breadth of the distribution, ⁇ r result from the analysis.
• the term "mean particle radius” is used herein instead of the more accurate term “mean equivalent hydrodynamic radius", which is the mean apparent radius. calculated from an experimentally determined diffusion coefficient, assuming spherical particles. ⁇ r as used herein is the standard deviation of the radius about r, assuming the particle size distribution is gaussian.
• the triacontanol particles must have a mean particle radius of less than 0.3 microns.
• the mean particle radius is prcferaoly less than 0.25 microns, and more preferably less than 0.15 microns, for greatest stability and highest particle number concentration.
• ⁇ r/r typically ranges from . 0.4 to .0.55.
• dispersions having acceptable stability can be obtained at values for ⁇ r/r up to 0.8.
• the particle size distribution would be large enough that a significant fraction of the triacontanol particles would flocculate. There is, or course, no critical lower limit on the value for ⁇ r/r since monodisperse systems, if they could be preparad, would be useful.
• the stability of the dispersions herein is also determined, in part, by the amount of the triacontanol present. Substantially. complete dispersion of triacontanol in water can be obtained at levels up to 0.5 g/1 of triacontanol. At higher levels, partial dispersion will occur but a significant, readily apparent, fraction will flocculate. It is believed that plant growth stimulation can be obtained, at typical application rates, at levels. down to 10 -10 g/1 of triacontanol.
• the present invention provides stable colloidal dispersions containing water and from 10 -10 to -0.5 g/l, preferably from 10- 8 to 0.4 g/1, and more preferaoly from -10 -5 to 0.25 g/l, of triacontanol. If the concentration of triacontanol exceeds 0.5 g/l, a dispersing agent is required to prevent excessive flocculation. However, even with the dispersing agent present, a significant fraction of the triacontanol flocculates if its concentration exceeds . 4 g/1.
• the present invention also provides stable colloidal dispersions containing water, from 10 -10 to 4 g/l, preferably from 10- 8 to 3 g / l, more preferably from 10 -5 to 1.5 g/1, of triacontanol and a dispersing agent.
• the dispersing agent is a preferred component for processing and handling reasons since it allows for the preparation of more concentrated dispersions (e-g., 1 g/1 of triacontanol) wnich can then be diluted with water or other suitable media (e.g., tne anti-freeze materials hereinafter described) to tne . desired triacontanol concentration prior to application.
• suitable media e.g., tne anti-freeze materials hereinafter described
• the use of a dispersing agent provides a significantly smaller mean particle size and higner particle number concentration at a given level of triacontanol.
• the dispersing agent can be any anionic, cationic, zwitterionic or polyfunctional single bond nonionic surfactant (semipolar nonionic surfactants are not useful herein). These surfactants are described by L aughlin in Advances in Liquid Crystals, Vol. 3, G. H . Brown (ed.), 1978, particularly from pages 61-66. - The phrase "polyfunctional single bond nonionic surfactant" includes the polyoxyethylene nonionics, polyol sugar monoesters, and the like. Amphiphilic structures, in which the polar, water-binding, hydrophilic group contains only hydroxyl and/or ether functional groups, must contain a multiplicity of these- functional groups to be operative as surfactants.
• the monohydroxy and monoether structures are not operative as surfactants, as defined by L aughlin in the above reference. Suitable surfactant dispersing agents are also described in U.S. Patent 3,929,678, Laughlin et al., issued December 30, 1975.
• Preferred dispersing agents herein have sufficiently high Krafft boundaries (e.g., greater than 10°C above the application temperature) that they will not form potentially phytotoxic concentrated surfactant solutions upon evaporation of aerosol sprays containing the dispersions.
• the most preferred dispersing agents herein are the sodium or potassium C 14 -C 24 alkyl sulfates, alkyl ether ethoxylate sulfates containing less than about 2 ethylene oxide units, alkyl glyceryl ether sulfonates and fatty acid soaps.
• An especially preferred dispersing agent is sodium tallow alkyl sulfate.
• the dispersing agent can be present at a concentration less than 50%, preferably less than 20%, more preferaoly less. than 2%, by weight of the triacontanol. Additionally, if the dispersing agent has a hydrocarbyl chain length ofeless than or equal to about 18 carbon atoms, it must be present at a concentration less than its critical micelle concentration (cmc) to prevent the micellar solubilization of the triacontanol. Micellar solutions of triacontanol are undesirable because they reduce the activity of the triacontanol, decrease the colloidal stability of the dispersion and precipitate relatively large triacontanol particles upon dilution.
• cmc critical micelle concentration
• Such a dispersing agent is preferably present at a concentration less than 0.25, preferably less than 0:1, times its cmc. If the dispersing agent has a hydrocarbyl chain length of greater than 18 carbon atoms, it generally must be used at a total concentration greater than its cmc in order to provide an adequate surface concentration to achieve colloid stability. (Because such long-chain surfactants are efficiently adsorbed at the particle/water interface, their solution concentration will usually be reduced to a value near or below their cmc). Within the above limits, it is generally preferred that the dispersing agent be used at its lowest effective level for stabilizing the dispersion since it can sometimes inhibit the growth stimulation benefits provided by triacontanol.
• the present aqueous dispersions will freeze over a very narrow temperature range. Freezing of the dispersions forces the colloidal triacontanol particles together and enhances flocculation.
• the present dispersions can additionally contain up to 40%, preferably from 10% to 25%, by weight of an anti-freeze material.
• Suitable anti-freeze materials include, for example, water-soluble alcohols such as methanol or ethanol, dipolar aprotic solvents such as dimethyl sulfoxide, and polyols such as ethylene glycol, propylene glycol, diethylene glycol, glycerol, erythritol, pentaerythritol, xylitol, and the various sugar alcohols.
• the anti-freeze material is preferably propylene glycol, glycerol, sorbitol or mixtures tnereof, and most preferably is propylene glycol.
• Tne stable colloidal dispersions of the present invention can be prepared by sonicating a mixture of the components (i.e., triacontanol, water, and optionally the dispersing agent and/or antifreeze material) at a temperature above the melting point of the triacontanol (ca. 90°C) until a staole colloidal dispersion is formed, and then cooling the dispersion produced to a temperature less than the melting point of the triacontanol. Tne triacontanol must be heated to above its melting point to be effectively dispersed.
• the components i.e., triacontanol, water, and optionally the dispersing agent and/or antifreeze material
• the mean temperature can vary slightly (e.g., 5°C) below the melting point while still providing dispersion.
• Sonication is generally described by Prakash, et al. in ultrasonics and Colloids, University of A llahabad, India (1961); in Sonichemical Engineering, American Institute of Chemical Engineers, H. S. Folger, (ed.), (1971); and by Reddy, et al. in the Journal of Colloid and Interface Science, 79:105-113 (1981). '
• sonication disperses the liquid triacontanol into extremely small particles by cavitation.
• the final triacontanol particle size is determined by the size distribution initially formed, whicn is influenced by the sonication conditions (i.e., time, wattage and number of cycles in continuous sonication), and by the rate of coalescence of the particles outside the cavitation zone.
• the coalescence rate is predictably decreased by dilution of the formulation to be dispersed, since there will be fewer triacontanol particles per unit volume of solution to coalesce, and by adsorption of the dispersing agent at the triacontanl/water interface.
• the dispersing agent creates an additional barrier to coalescence which is probably electrostatic in nature when the dispersing agent is an ionic or zwittsrionic surfactant, and is possibly steric in nature when the dispersing agent is a poly functional single bond nonionic surfactant. It is believed that the semipolar surfactants (e.g., amine oxides, phosphine oxides) are not effective dispersing agents because tney are small, weakly polar nonionics not capable of stabilizing colloids by the steric mechanism. The stabilization of colloids by electrostatic and steric mechanisms is described by Ottewill in Nonionic eurfactants, M. J. Schick (ed), Ch. 19 (1967).
• Tne present invention also encompasses methods for stimulating plant growth by applying thereto an effective amount of the staole colloidal dispersions herein.
• the of application to plants can oe by any convenient form, such as oy seed soaking, dipping, foliar spraying, soil drenching, or the addition of the dispersion to irrigation water or a nutrient solution.
• the time of application can also vary considerably in that the dispersion can be applied to seeds, seedlings or the leaves or roots of growing plants.
• the spray generally should contain from 10 -8 to 10 -3 g/l, preferably from 10- 7 to 10 -4 g/l, of triacontanol.
• the dispersion is preferably applied in the field at a rate which provides from 10 -6 to 1 g/ha, more preferably from 1 0 - 5 to 10 -2 g/na, of triacontanol
• the purity of the triacontanol can significantly affect its ability to stimulate plant growth.
• the triacontanol used herein is preferably greater than 97% pure, and more preferably greater than 99% pure.
• Triacontanol of acceptable purity can be synthesized by the process described in U.S. Patent 4,268,697, Gibson, issued May 19, 1981, particularly in column 3, lines 54-59.
• the dispersions herein are useful for stimulating growth in a wide variety of plants. They are especially valuable for increasing yields in agricultural crops such as corn, soybeans, wheat, milo, rice, tobacco and cotton, and in truck crops such as tomatoes, asparagus, lettuce, oeans and the like.
• the dispersions should also be useful for stimulating growth. in trees, herbs, flowers and houseplants.
• a stable colloidal dispersion of triacontanol was prepared by batch sonication as follows.
• Apparatus A Heat Systems - Ultrasonics, Inc. Sonifier - Cell Disruptor, Model W158, with a stepped titanium microtip (0.32 cm tip diameter) was used.
• the 25 ml sonication vessel was conical, but with a flattened bottom, and contained a thermistor well flush against the side. It was connected by a spherical joint (unlubricated) to a short condenser having a threaded Teflon cap.
• the cap had an 0-ring-fitted hole through which the wide upper part of the sonication horn could be inserced. during use, the tip was 1-2 mm from the bottom of the vessel.
• the condenser (with cooling water) was attached, the tip inserted, and the thermistor of a digital thermistor thermometer inserted in the well..
• the sample was heated to about 60°C using an oil bath maintained at 85°C, at which point the sonifier was turned on.
• the power setting was adjusted to ca. 40 watts.
• the sonication rapidly brought the temperature to 90-92°C; it was held there, by adjusting depth of immersion in the bath, for a period of five minutes.
• the original high turbidity decreased during this period to the point that the tip became clearly visible.
• the vessel was then immersed in a beaker of water, dropping the temperature rapidly to ca. 65° C , at which point the sonifier was turned off.
• the condensate on the condenser walls was rinsed back into the vessel using a Pasteur pipette and the contents of the vessel.
• the condenser was then removed and the product, a uniformly hazy dispersion, decanted into a storage vial.
• the triacontanol had a mean particle radius r of about 0.215 microns and a ⁇ r of about 0.103 microns.
• a staole colloidal dispersion of triacontanol was prepared by continuous sonication as follows.
• a Branson Sonifier Cell Disruptor Model 350, with a Heat System - Ultrasonics Cat. No. 200, 1.27 cm disruptor horn and Model 800B Continuous Flow Cell (stainless steel) was used.
• the cell was modified by replacing the stainless orifice plate with a teflon plate (0.16 cm hole) and by. replacing the 0-ring under the plate and the 0-ring which sealed the orifice holder to the body tube with machined Teflon gaskets. After performing these modifications and passivating the cell by sonifying 0.01 N N 2 SO 4 in the cell at 90°C, pure water could be recirculated through the cell without apparent change in turbidity. The original 0-ring seal between the body tube and the thick upper part of the disruptor horn was left intact.
• the sample port near the orifice plate was fitted so that a stainless steel jacketed thermistor probe could be sealed in this port.
• the thermistor was inserted to a point near but not touching the horn.
• the chamber volume of the flow cell was 62 ml.
• An FMI valveless reciprocating piston metering pump (FMI Model #RP-G150-1-CSC) fitted on the outlet with a tee holding a 4-5 cm sealed glass header tube and a needle valve was used to meter the dispersions through the flow cell. By adjusting the needle valve so that a back pressure of 1-2 atmospheres developed in the header, the pump surge was effectively eliminated.
• the outlet was connected to tne flow cell sample port remote from the orifice plate using 0.16 cm CTFE tubing and stainless ferrule fittings; the pump inlet was similarly connected to the reservoir container.
• the titanium tip was removed and polished using fine emery cloth on a flat surface until smooth. It was weighed before and after sonication of the six batches. The customary pitting in a zone parallel to the edge of the tip and about 1 mm in was observed, but the weight loss was less than 1 mg. It was repolished prior to' each continuous sonication run.
• Continuous sonication was performed by pumping the coarse dispersion through the cell at a nominal rate of 10 ml/minute, keeping the cell temperature between 90-91°C.
• the first 130 ml (ca. two chamber volumes) were remixed with the coarse dispersion before collection commenced.
• nine 250 ml aliquots were collected over a period of 218 minutes (10.3 ml/min).
• Turbidity readings were taken using a Bausch & Lomb Spectronic 20 set at 580 microns and a 1 cm cell.
• the approximate mean particle radii, inferred from other data on turbidity versus mean particle radius, were as follows.
• the product was relatively uniform.
• the combined fractions were resonicated as above, collecting 2100 ml in 205 minutes (10.2 ml/min).
• the chamber contents were added to the product to yield 2160 ml of a stable dispersion of triacontanol.
• the dispersion contained 927 + 27 mg/l of triacontanol and 12.6 + 0.4 mg/l of T AS.
• the triacontanol had a mean particle radius, r, of 0.105 microns and a ⁇ r of 0.059 microns.
• the above dispersion can then be diluted with water to a triacontanol concentration of 10 -3 g/l and distributed to the ultimate user. After again being diluted with water to a concentration of 10 -6 g/1, the dispersion can be sprayed onto plants in the field at a rate of 100 1/ha to provide sufficient triacontanol ( 10 -4 g/ha) to stimulate plant growth and crop yields. Similar results can be obtained when the dispersion is applied at rates which provide 1 0 - 5 or 10 -3 g/ha of triacontanol.
• dispersions of the present invention can be prepared by the methods described in Examples I and II when the sodium tallow alkyl sulfate is replaced with sodium eicosyl ethoxylate (2 avg.) sulfate, potassium tallow alkyl glyceryl ether sulfonate, sodium stearate, sodium C 12 linear alkylbenzene sulfonate, cetyl trimethylammonium bromide, 3-(N,N-dmethyl-N-coconutalkylammonlo)-2-hydroxyprorane-1-sulfcnate, 2-trimathyl-ammoniohexadecanoate N-tallow allkyl-N,N-dimethylammonioacetate, the condensation product of a C 10 linear aliphatic alcohol with about 5 moles of ethylene oxide, the condensation product of a C 9 linear alkyl phenol with
• dispersions herein can be prepared by-the methods descrihed in Examples I and II when the concentration of triacontanol is 10 -1 g/l or 3 g/l, or when the weight ratio of triocontanol to dispersant is 1000:1 or 100:1.
• Dispersions of the present invention can also be prepared by the above methods when the concentration of triacontanol in water is
• Triacontanol was dissolved in acetone, Tween 20 and Tween 80 at concentrations of 1000 mg/l. The solutions were then poured into distilled water to form the indicated concentrations of triacontanol. None of the samples were completely dispersed; all displayed visible flocculation.
• the mean particle radius, r, and ⁇ r were determined as follows.

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• 1981
  • 1981-11-09 US US06/319,565 patent/US4420329A/en not_active Expired - Fee Related
• 1982
  • 1982-06-09 EP EP82200708A patent/EP0067484A1/de not_active Withdrawn
  • 1982-06-11 AU AU84801/82A patent/AU8480182A/en not_active Abandoned
  • 1982-06-14 ES ES513057A patent/ES8307695A1/es not_active Expired
• 1983
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